I almost got banned from high school chemistry for making this (UK 1970's). Made it during break in middle of Chemistry lab while the teacher was out, and sadly

I almost got banned from high school chemistry for making this (UK 1970's). Made it during break in middle of Chemistry lab while the teacher was out, and sadly was rather sloppy - got it over the floor, threw damp filter paper covered in it into the waste paper basket (which later self-detonated), etc.